Hydraulic device



June 22, 1965 H. MOLLY HYDRAULIC DEVICE Filed Dec. 21, 1961 4 Sheets-Sheet 1 Fig. 1

PRIOR ART Fig. 2'

PRIOR ART Fig. 3

[N V EN TOR.

jfams Mai/g0 June 22, 1965 MOLLY 3,190,186

HYDRAULIC DEVICE Filed Dec. 21, 1961 4 Sheets-Sheet 2 I 1 44 44s I I 5-51 1f #6 d I 7 8| 58d y 4 mu 44 43 55 5 59 35A Q 3 7 x I U 13- J INVENTOR. )(cZ/YS wax/y June 22, 1965 H. MOLLY 3,190,186

HYDRAULIC DEVICE Filed Dec. 21, 1961 4 Sheets-Sheet 3 I I/l Fig.9 24 1 3 8 IN V EN TOR.

ya 22; War/[y pa/4 PM a? MWW June 22, 1965 Filed Dec. 21, 1961 -37 -2- J T O liven/ 01 715L115 mg; 2

4 SheetsSheet 4 United States Patent 3,19%),186 HYDRAULIC DEVICE Hans Molly, 48 Dr. Eugen-Essig-Strasse, Malsch,

Kreis Karlsruhe, Germany V I Filed Dec. 21, 1961, Ser. No. 161,116 Claims priority, application Germany, Dec. 27, 1960,

21 Claims. (Cl. 91-382) The invention relates toa hydraulic lifting device, more particularly for plow depth control.

Prior art To aid in understanding the advantages and improvements of the present invention, a summary of related prior art devices is presented.

Devices for plow depth control are known where the plow due to a corresponding design of the plow share and correspondingly existing plowing depth. In the first .in-

stance the plow is lifted relatively to thetractor, in the latter case the plow is lowered relatively to the tractor,

which is achieved by supplying oil to the jack or by draining the oil therefrom respectively. With the plow depth control devices operating in accordance with this principle an oil supply to the jack is only required for correcting the depth deviations from the theoretical value. If an expensive and complicated pump with variable capacity shall be avoided, there is however a constantly continuous oil flow which e.g. is produced by a gear pump. Now, in the simplest manner possible, the arrangement may be so designed as described in FIG. 1. A constantoil flow is supplied to line 1 by a gear pump. From line 1a line 2 is branched oif which over a spring-loaded back-pressure valve 3 leads to the working piston. Line 1 leads to a distributing slide valve 4 which with two guiding edges 5, 6 controls the connection of line 1- -over line 7and a, line 8 branched off behind the back-pressure valve 3 With the outlet 9. The distributing slide valve4 is moved to the left into position Lower by adequate means, e.g. in accordance with the existing pull, to the right into position Lift. In the illustrated position Stop the full oil quantity supplied to line 1 flows olf through line 7. Line 8 is shut off and a back-flow of the oil in the work- This tendency is counteracted by.

ing piston is prevented by the back-pressure valve 3. Thereby the plow is so-to-speak rigidly connected'with the tractor. If the distributing slide valve is shifted to the left, the guiding edge 6 releases channel 8 so that oil may flow off from the jack and the plow is lowered. If, however, the distributing slide valve is shifted to the right into position Lift, channel 7 is shut ot i so thatwith not completely release channel 7 after the lifting of the plow, so that. the illustrated Stop position is resulting.

The plow is rather only lifted until the guiding edge 5 3,199,185 Patented June 22, 1965 "ice somewhat releases channel 7 and the impact pressure at the so-resulting throttle corresponds to about the plow weight effective with this depth, so that the Working piston does not move any further and consequently also the distributing slide valve remains in its throttling position. Thus the full oil flow is contantly flowing through the relatively small throttle opening, which may very quickly lead to an inadmissible heating of the oil.

These disadvantages shall be avoided by an arrange.- ment also known, presented in FIG. 2. Therein, the connection of line 1 to the outlet 9 is not directly controlled by the distributing slide valve This connection is rather established by a line It being controlled by a control valve 11. This valve 11 is loaded by a locking spring 12. Besides, the pump pressure acts in an opening sense. By means of the distributing slide valve 4 in the right Lift position the pump pressure is guided to the-reverse side of valve 11, that is to say acting in the direction of spring 12, over a line/13. Then, the pump pressure acts on the valve from both sides so that valve 11 is kept shut by V the spring 12, independently of the fact how much the pump pressure increases. By the lifting of the plow the distributing slide valve is shifted to the left until the guiding edge 6 connects the channel 13 with the outlet 9; This does not as yet directly affect the acting pumppressure so that the deleterious etlec't described in connection with FIG. 1 does not occur. By the connection of line 13 with the outlet 9 valve 11 is only impinged upon by theoutlet pressure on the spring side, so that the high pump pressure rapidly overcomes spring 12 and the pressure chamber of the pump is connected with the outlet over line ll). The back-pressure valve 3 closes and the lifting movement is interrupted. Then, no oil flow is constantly flowing through a narrow throttle as with the mentioned arrangement (FIG. 1). established rather unimpededly, apart from the fact that valve it maintains a minor overpressure determined by the force of spring 12 of eg 2 atmospheres excessive pressure in the system. Thus, practically no heating or" the oil takes place. The lowering action takes place correspondingly. In practice,,this arrangement has shown the'disadvantage that the adjustment of the plowing depth always takes place intermittently, just as intermittently as valve 11 opens and closes. This leadsto undesirable shocks which, besides, cause a strong Wear.

, Rszt'm of the present invention ventionthis object is attained by providing that the jack is connected with the pump chamber over the distributing slide valve having a throttle cross-section depending on the position of the distributing, slide valve and that the pump pressure supporting the load-spring, is derived behindthe throttle cross-section. Then, control valve 11 in connection with the throttle acts as quantity .(fiow) control by keeping the differential pressure at the throttle on a constant value determined by the force of spring 12. By varying the throttle cross-section in dependence on the position of the distributing slide valve, the theoretical value of the quantity control is continuously varied and V therewith the adjusting speed of the working'piston;

Thereby it is achieved that the latter steadily adjusts to itsncwposition, when there is an interference, andan intermittent adjustment of theplow is avoided. The other functionsof the'valve are maintained. With the adjustment of the distributing slide valve into the position Stop, the outlet pressure is fedbehi-nd the control valve so that it completely opens and only acts as pressure control. The essential point is that the throttle cross-section does not'become Zero so that the working piston per- The connection to the outlet is a forms its lifting- -even if with decreasing speed-until the distributing slide valve establishes this connection.

A control valve must easily operate. the. arrangement may be so provided that the connection controlled by the valve between pump pressure chamber and outlet can be additionally tightly shut-oflE by the distributing slide valve. Then, thefit of the valve need not For this purpose be very narrow since an additional shut-E is performed.

by the distributing slide valve in its end position. expedient having the control valve designed as piston valve and centrally loaded with pointcoutact by the load spring, eg by pressing the load spring on a spring plate whichabuts the conically designed end of the plunger The spring force consequently acts exactly centrically on the piston. i

In order to obtain a flatter control characteristic of the piston valve the arrangement may be so provided thatthe plunger is designed as trunk piston open to the pump; pressure chamber, having control openings on its' skirt;

wear would be caused. For this reason the valve may be 7 so designed that the secantial control openingsare covered again in] the open-position of the valve.

With hydraulic lifting devices of. the present type it may occur inextreme cases that the lifting ofthe jack is not suflicient to balance an interference (e.g. increased pull of the plow). In such a case the distributing slide valve remains in its position Lift, so thatoil is constantly supplied to the jack even if the working piston is already in its end position; The pressure increases stronglyand extremely largeforces might occur which may lead to a damage of the device. In order to avoid this,- a safety valve may be provided whereby when a certain high pressure is exceeded in the pump pressure chamber the latter is connected with the outlet. Since such a safety valve is by nature loaded witha very strong spring, then the full 'oil flow supplied .by the pump, strongly throttled flows through the safety valve. This causes a quick heating of the oil with all its deleterious effects. In order to avoid these disadvantages, in further modification of the invention an adjusting movement derived from the lift of the the lifting speed Gil working piston can be additionally intruded on the distributing slide valve, which interrupts the -oil supply to the jack in the end position of the Working piston. This may be attained byproviding that the distributing slide valve in a mannerknown as such is designed as control piston axially movable transverselyto the axis of the working piston and is displaceable by means of an inclinedsurface or cam on an end-position feed-back member moves by the working piston. This cam protrudes devices.

4. pressure valve may be inserted in the distributing slide valve in a manner known as such. Then, all valves are combined in-the distributing slide valve while the distributing slide valve casing alone. contains the difierent connecting channels.

The arrangement may be so provided that a channel controlled by the back-pressure valve,'of;the distributing slide valve is connectableto the differentworking chambers depending on the position of the distributing slide valve, by optionally connecting the channel controlled by the back-pressure valve. with the one or the other side of a double-acting working piston. Then, advantageously the distributing slide valve is so designed that the throttle cross-section of the distributing slide valve is increased. with the adjustment of the distributing slide valve from a 1 Then the .working y middle position toboth directions. piston may. be reversed from pressure to. pull whereby with zero passage decreases; to a mini-1 mum value. g V Of course, this insertion of the valves in the control piston is not defined to valves which act'as quantity control valves in the above described manner according .to

the invention, but, of course, also applicable with snap action valves of the described known type. Here, the;in-. sertion offers the particular advantage that an additional shut-off of the outlet channel is possible which is of special significance with thenecessary easy operation of the control valve. t I

The invention is explained by means of a plow depth control. his obvious that they applicability of the inven:

tion is not limited to plow depth controls but that the invention may be applied to the most different hydraulic Embodiments of the. present invention A few embodiments of the invention arepresented in the drawingsand described as follows:

. FIG. 3 schematically shows a lifting device. according to the invention corresponding to FIGURES 1 and 2 dealt with in the beginning.

FIG. 4 schematically. shows a modification of the ari rangement according toFIG. 3.

FIG. 5 similarly schematically shows a third embodiment of the invention.

FIG. 6.shows the structural design of an arrangement according to the invention-in sectional 'view, which has been especially adapted for a plow depth control.

what modified relatively to FIG. 6.

FIGURES 11 and 12 showthe longitudinal and'crossi section of a plunger of the control valve.

into a cavity-of the control piston, with the cavity being in communication with the jack. Thus, no seal is required when the end-position feed-back member exits from the jack. 7

- Besides, the safety valve maybe so arranged that on its response the high pump pressure is'fed behind a front surface of the distributing slide valve in such a manner that it feeds back the distributing slide valve into the Stop 'position.- i

Itis a further object of the invention with such and similar hydraulic control devices to simplify the design and make it more compact. According to the invention this object is attained by providing that the valve controlling the connection between pump pressure chamber and outlet is inserted in the distributing slide valve. Then the distributing slide valve together with the shut-oft or con trol valve, respectively, constitutes a single compact unit. I

i In furthermodification of the invention also the back- FIG; 13 shows a modification of the arrangement ac-. t cording to FIGURES 7 to 1$) with a double-acting v'vcirking piston.

' The embodiment according. to FIG. 3 substantially-corresponds to-the arrangement'according to FIG. 2 Like.

reference characters denote" like parts. Line Zleading to jack 14 (FIG. 2) .over.the check valve 3 is, however-,: I not directly branched off from line 1, but from the control chamber 27. of the distributing slide valve .4 behind a. throttle 15 comprising a throttle cone or boss :16 0f the distributing slide 4'and the distributing slidevalve casing. The cross-section of throttle 15 varies in depend-;

ence on the position of the distributing slide, but never In the position Stop,- the chamber containing spring,

12 behind valve 11 is connected jwith t-he outlet 9 'over line 13. Valve .11 is therefore pressed open abythe:

. line 10. Check valve .3 is closed. If the pull of the plow increases, the distributing slide valve is moved 10 becomes zero. Line 13 is branched oif behind'thethrottle.

the night so that the pressure in chamber 27 behind throt tle 1-5 acts on valve 11 over line 13. Thus control valve 11 then closes under the influence of spring 12. With control valve 1:1 closed the pump pressure increases, checkvalve 3 opens and oil is supplied to jack 14. Since this oil flows through the throttle, a dynamic pressure dilferential exists thereat which also becomes efiective at control valve 11 over line 13. Consequently, it is not the same pump pressure that acts on the valve from both sides, but a pressure dilferential. The valve is consequently opened alittle so that a portion of the supplied oil quantity flows to the outlet over line and the pressure difierential at throttle correspondingly decreases. Then a state of balance exists in which the pressure differential at the control valve 11 and consequently also at throttle 15 is counterbalancing the force of spring 12. .Thus the pressure differential at the throttle is kept constant and therewith also the oil flow per second through the throttle. Thus, throttle 15 together with valve 11 operates as quantity (flow) control, the principle of which is known vas such. Since the throttle cross-section varies in dependence on the position of the distributing slide valve 4, therewith also the theoretical value of the quantity control varies. The oil quantity, so adjusted, however, controls the adjusting speed of the working piston.

=Assuming that the plow has dug very deeply into the soil and consequently a strong pull occurs in the plow support. This would cause arelatively substantial movement of the distributing slide 'valveto the. right. Then,

tity of oil flows to jack 14 so that the plow is relatively quickly lifted in the beginning. With it, however, the pull decreases and the distributing slide valve piston 4 moves to the left. Thereby the throttle cross-section is decreased so that the lifting movement gradually becomes slower the more the plow approaches the desired depth until it is finally lifted with a minimum speed determined by the minimum cross-section of throttle 15. With a corresponding speed also the distributing'slide valve 4 moves further to the left until it connects channel 13 with the outlet 9. Then control valve '11 is suddenly opened, as is well-known, so that the lifting movement is interrupted. If the plow is too high, that is to say the pull becomes too small, the distributing slide valve moves to the left so that the control cylinder is connected with the outlet .over line 8. In FIG. 4 an embodiment is shown where line 8 is eliminated'and instead the check valve 3 designed as disk valve which is pressed open by means of a valve rod by a truncated conical face 17 of the distributingslide valve 4 when the slide is moved to the left to release fluid from the jack. The other function is the same as with the embodiment according to FIG. 3.

FIG. 5 shows an embodiment where control valve 11 is arranged in the distributing slide valve 4. The same referencecharacters as in FIG. 3 denote corresponding parts. Line 13 positioned here in the distributing slide 4- of the valve, opens: into a longitudinal groove 17, which depending. on the position of the distributing slide valve is inrcommunication with the control chamber 27 behind the throttle. 15 or. with an annular chamber 18.

Chamber 18 is connected with the outlet over a part of line 10. This results in a favorable compact unit where practically all par-ts are combined in the distributing slide valve. Besides, channel 10 may favorably be shut-off by the guiding edge 19 in the end position of the distributing slide valve 4. Thereby valve 11 need not be designed so as to be absolutely tightly closing, but the fit may be relatively wide so that the valve operates easily. This embodiment in its operationalso corresponds to the embodiment according to FIG. 3.

FIG. 6 shows a structural design of the arrangement according to FIG. 5. V

In a valve casing 21 the distributing slide 4 is guided the throttle cross-section is very great and a large quanin a transverse bore 23 or body 21 and is displaceable by a rod 22.. An inlet channel or connection 1 opens into bore .23 and is connected to the pressure chamber of a gear pump not shown here. The return connection or channel 9 and the jack connection or channel 2', which is in connection with jack 14, also communicate with bore 23. Outlet channel 2 contains the check valve 3 inserted in the distributing slide valve 4. Channel 2 is partially in the distributing slide 4 and partially in the distributing slide valve *casing'Zl and includes transverse bores 2', which opens into an annular groove 2" of the distributing slide valve 4. Channel 9 opens into an outlet chamber 24 at one end of bore 23 and sealingly shut-off to the outside by a plug 25. One end of the distributing slide 4 protrudes into the outlet chamber 24. The portion of the slide 4 to the right of cham- "ber 24 (as seen in FIG. 6) is sealingly guided in'the Channel 2 opens into an annular control cham- To the right.

the distributing slide 4, however, a certain minimum cross-section is a'lways maintained. 7

The distributing slide 4 has a blind-end bore 31 closed by a cap 32. A plunger 11 is guided in bore 31, de-

signed as a skirted piston with the external portion of the piston head beingconical. Spring 12 acts on the 'peak of this cone over' a spring plate 32". The plunger 11 controls a lateral outlet 33 of bore 31, which opens into chamber 24. In the shut-off position of the valve, piston 11 abuts a shoulder 34. Piston 11 divides the bore 31 into two chambers: one chamber 35. receiving spring 12 and closed 05 by the cap 32, and which in the following will be designated as the spring chamber,

and a chamber 36 to the right of the piston 11 in FIG.

6, which is designated as the. pressure chamber. Pressure chamber 36 is in communication with the intake chamber 28 through a' lateral bore 37. Always the full pump pressure prevails therein. Spring chamber 35 is in connection either with the outlet chamber 24 or with the annular control chamber 27 over'a longitudinal bore 13, corresponding to channel 13 in FIG. 5, and two. an-

nular grooves 38, 39 depending on the position of the v,

distributing slide valve 4.

:For flattening the control characteristics of the control valve the oil escapes through lateral holes 41 inthe skirt of the piston 11, at least some of which always are in registry with opening 33 when the slide valve is directing hydraulic fluid to the jack. Holes 41 are secantially drilled as can be distinctly seen in FIG. 12, so that the oil secantially escapes and makes the piston 11 rotate. Thereby the friction is decreased.

A safety valve 44 is connected tothe intake line 1, and has a strong spring 45,'which blows oil when overpressure occurs, eg if the lifting action is stuck, over line 43 into chamber 46. Thereby a balancing piston 58'moves back I to the position Stop against the pressure of a Weak spring 57. The oil pressure in chamber 46'moves the distrrbut-ing slide valve 4 to the left from the lift position against the pressure of a stronger spring 59 to approxi-.

mately the FIG. 6 position at which oil from inlet channel 1 will flow to outlet channel 9, whereby the blowing-off action of the safety valve is terminated. Possibleroil continuing toescape from the safety valve flows off over edge 69. After the introduction of a lowering movement by red 22 moving slide valve 4 to the left the balancing piston 57 presses somuch oil out of chamber 46 over edge 69 that the distributing slide valve can again be moved to:

. wards Lift.

Safety valve 44 comprises a sleeve 44:: having a central bore within which is received a piston 44b. Piston 44b I 7. 1 is connected to a stop rod 44c. The stop rod 440 has a flange 44d against which spring 45 bears'to urge the piston 44b and the. stop rod to the left into its cylinder. Sleeve 44a is held in position by a spring ring 44a. Sleeve 44a defines an annular groove 44] thereabout. Lateral bore =holes 44g provide communication between the annular groove 44] and the central opening occupied by piston 44b. Passageway 43 communicates with the annular groove 44 and with chamber 46. A passageway 58a cornmunicates with passageway 43 and with cylinderSSb with in which piston 58 is positioned.

When excess pressure has developed as hereinbefore mentioned,-that pressure moves piston 44b. to the right in .FIGURE 6 against the resistance of spring 45. The latter -movement uncovers lateral bore holes 44g so that the oil ,may escape through passageway 43 and into chamber 46 intake conduit 1 is relieved, safety valve 44 closes and slide'valve 4 moves to the, FIGURE 6 position under the influence of spring 59. In this position, communication 'at' 69 between chamber 46 and chamber 54 is shut on. To relieve the hydraulic blocking of. slideyalve 44- that then occurs, rod 22 is moved to the left in FIGURE 6 moving the slide valve sutficiently to uncover edge 69 and permit excess oil to be expelled'from cylinder 58b under the influence of spring 57. r p

In normal operation thereafter, hydraulic blocking of slide valve 4 will, tend to occur when the parts are in the FIGURE 6 position and closed chamber 46 is cutoff from chamber 54. However, should it be desired to move the slide valve 4 to the right to the Lift? position (to the right in FIGURE 6), hydraulic blocking is prevented by expansion'of the exposed volume in cylinder 58b. Thus as rod 22 is moved to the right, spring .59 urges slide valve 4 to the right. Excess oil in chamber 46 is forced through passageway 43, passageway 58a and into cylinder 58b. This oil moves piston 58.to the left against the resistance of spring 57 to prevent any hydraulic blocking of slide valve 4. This mechanism is provided since rod 22 is in a fluid tight chamber, only a portion of which is'illustrated at46'. V

i The casing 21 forms a piston head shutting off the jack 14 on one side and the distributing slide valve 4 extends transversely to the aXis of the jack. Channel 2 is elongated in the axial direction of the cylinder of the jack across thedistributing slide 4, i.e. defines an opening through the slide. At this opening the slide has'an inclined surface 48 forming a cam follower. Anobliquely deflected end of a feed-back rod 49 forms a cam to oper- --preferably manually. The distributing loose fit of valve 11, can be shut oif. Throttle .15 is widely opened and practically not efiective anymore; Thus the full oil flow is flowing 3 pressed open.

FIG. .8 shows the position Lift at a substantially slower rate. Here, throttle 15 is effective.- The throttled.

pump pressure is fed into the spring chamber 357st control valve 11 fromcontrol chamber 27 through channel 13. The full pump pressure is fed into pressure chamber;

covered so that the" piston 11 ceases rotating. ,7 Since now a direct connection between pump pressure chamber and outlet exists, the pump pressure breaks down. Valve 3 closes and the working piston of the jack remainsi n its position. a

FIG. 10 shows the position Lower. Here, too,-the connection between pump pressure chamber and outlet is maintained. a In addition, the outlet channel8 (formed by chamber 54, conduit 55 and chamber 24 in FIG. 6)is re-.

leased so that oil from jack 14 may flow to the-outlet.

FIG..13 shows a device for controlling a double-acting piston 60. 'The transversebore 2' .is connected with a channel 61*orachannel 62 depending onthe position of the distributing'slide valve, one of which opens-into .jack- 14 on the one side, theother on the other side .of

piston 60. Here, the throttlecomprises a double-cone 63 of the distributing slide valve 4 and a throttle ring 64".

This results in the fact that the piston 60 adjusts'to-the jack 14 is connected with. the outlet channel .8 over ate slide 4. Rod 49 is guided in abore 51 of the working piston 52. Shortly before reaching the fully'extended position of the working piston 52 rod 49 is carried along .by a stop 53 of the piston 52. The deflected end of the r.

.rod 49 thereby presses inclined surface 48 and moves the.

distributing slide .4 to the left to interrupt the'oil supply to the working piston. In the position of slide 4 illustrated in FIG. 6; chamber 46 is sealed against a chamber '54 by a guide 4 0f the distributing slide 4. Chamber 54 is connected with theoutlet 9 over a bore 55 and outlet chamber '24. Thereby oil leakage losses areavoided in the Lift channels 61 or 62 respectively.

Iclaim:- A r 1. In a hydraulic control apparatus for use witha hydraulic jack and a hydraulic pump and'including'a slide I valve witha'pumpf connection, a jack connectionfand .a .returnconnection with the slide valve being axially movable in the valve body whereby atone slide valve setting the pump connection is placedin" communication withi'the jack connection through a passage having a check valve therein, at a second .valve setting the pump connection issufiiciently cut off from thejack' connection to prevent actuation thereof and at a third valve setting the jack is discharged to the 'fluid return connection, the improvement comprising:- a throttle between 'saidfplimp connectionw and said passage; a control valve including ja cylinder with a piston movable 'the'r'einfand resiliently urgedto a seated position in the cylinder, said ipistondividing said cylinder into two chambersjone-of said vchambers having two openings'th'erein, one of said openings communicating with said pump connection "andthe other ofthe openin'gs communicating withthe return connection, said piston cutting ofl communication between-the openings when. in.

seated position, said one opening being positioned so that the pump pressure acts on the piston in a direction to uriseat said piston against said urging, the other chamber having an opening therein; and means connected to the latter opening to place it in communication with said passage when the slide valve is in the one, setting and to slide valve is adjusted to this position, e.g. if the plow shall be lifted. when turning round. In this position the outlet,9 is 'shut-' off-by the control valve .11 since this is impinged upon: on both sides with the full pump pressure and closed by the spring. In addition, opening 33-is closed by the guiding edge 26 so that possible oil leakage quantitiesdue to :a.

to the jack through .valve 1 place it in communication with the return connection when the slide valve is in another position.

2. In an apparatus as set forth in claim 1, wherein said throttle is defined by a :boss on the side of the slide valve and the surrounding valve body, said boss being tapered axially of the slide so that the size of the liquid opening thereabout is increased as the slide is moved from the second toward the first setting.

3. In an apparatus as set forth in claim 2, wherein said piston includes a piston head and a skirt extending therefrom, said piston being positioned in said cylinder with the skirt being on the one chamber side of the head.

4. In an apparatus as set forth in claim 3, wherein said head is convex on the side thereof opposite said skirt, and said resilient urging is provided by a spring in the other chamber, said spring applying force to the central part of said convex head.

5. In an apparatus as set forth in claim 4, wherein a spring plate is interposed between the convex head and the spring with substantially a point contact between the plate and the head.

6. In an apparatus as set forth in claim 3, wherein the. other of said openings is in a sidewall of thecylinder, and said skirt has a plurality ofsecantly arranged openings thereabout and adapted to be'aligned with the other opening in one position of the piston, whereby a force tending to rotate the piston in the cylinder is applied to the piston by the flow of fluid through the piston openings and into said other opening.

7.In an apparatus as set forth in claim 6, wherein said secantly positioned openings are so positioned with respect to said other opening so as to be covered by the cylinder wall both in the seated and the fully open positions of the piston and to be exposed at said other opening only in an intermediate position of the piston.

8.111 an apparatus as set forth in claim 2, wherein said piston includes a piston head and a skirt extending therefrom, said piston being positioned iii said cylinder with the skirt being on the otherchamber side of the head, and said resilient urging is provided by a spring in the other chamber and bearing against said head.

9. In an apparatus as set forth in claim 1, wherein means operatively interconnects theslide valve and the jack to move the slide away from said one setting as the jack approaches its fully extended position.

10. In an apparatus as set forth in claim 9, wherein said slide valve is resiliently urged in the direction toward said one setting, said slide has a cam follower'facing in said direction, and the last mentoned means includes a cam facing in the reverse of said direction and connected to the jack to contact the follower and move the slide against the urging as the jack approaches the fully extended position. a

11. In an apparatus as set forth in claim 1, wherein said cylinder is an integral part of the slide.

12. A hydraulic control apparatus for use with a hy-' draulic jack and a hydraulic pump supplying. hydraulic fluid under pressure, said apparatus including: a valve body member having an axial opening for a slide, a fluid pressure connection for connection to said pump and communicating with said opening at a position therealong, an enclosed chamber extending outwardly from the opening and axially spaced from said position, a fluid return connection communicating with said opening and a jack connection; a slide member in said opening and movable axially therein between a first general position at which said pressure connection is in communication with said chamber and a second general position at which said chamber is 'substantially 'cut off from said pressure connection; said members including a throttle device eifective to increase the extent of fluid communication between the pressure connection and the chamber as the slide member is increasingly moved toward the first general position from the second position; a fluid passageway in at least one member between the chamber and the jack connection; a check valve to normally prevent the flow of fluid through the passageway in the direction of from the jack connection to the chamber; a control valve'in one of said-members and including a cylinder with a piston therein dividing said cylinder into a pressure chamber and a spring chamber, said cylinder having pressure opening and a port therein in the pressure chamber, resilient means urging said piston into seated position at which said pressure opening is closed and said port is at least substantially closed; a passageway connecting said pressure-opening andsaid pressure connection; means in at least one member defining a passage between the'spr-ing chamber and the enclosed chamber when the slide. member is in the first general position and between the spring chamber and the return connection when the slide memher is in another position; and a passageway connecting the port and the return connection.

i 13. An apparatus as set forth in claim 12, wherein said control valve is an integral part of the slide member.

14. The combination of a hydraulic jack and a slide valve therefor, said combination including: a hydraulic cylinder; a piston movable axially in said cylinder; a'

cylinder head member closing one end of said cylinder,

said head having a first opening therein for a valve slide and positioned at an angle to'the line of movement of the piston, a second opening between said first opening and'said cylinder, a pressure line connection communicating-with said first opening, and afluid return connection communicating with said first opening; a slide member in said first opening and movable longitudinally therein; resilient means urging said slide member in a given direction in the first opening; means operatively connected to the slide member and extending outside the head member to permit said slide member to be moved in the reverse of said direction against said urging; said members including fluid control means to direct the flow of by draulicfluid from said line connection to said second opening when said slide is in .a first position, to direct the flow of hydraulic fluid from the second opening to the return connection when the slide is in a second position and to prevent the flow of fluid to and from the second opening when the slide is in a third position, said first position being in said direction from the second position; a cam follower connected to the slide and positioned in said second opening when said slide is in the first position, said follower facing in said direction; and a cam operatively connected to said piston and positioned in said second opening, said cam being positioned to contact said follower and move said slide away from the first position when said piston reaches approximately the end of its stroke.

15. The combination of jack and valve of claim 14,

wherein the fluid control means includes a check valve withinthe slide member and effective when the slide is in the first and third positions to prevent the flow of fluid from the second opening toward either of said connections.

16. The combination of jack and valve of claim 15, wherein said fluid control means includes a by-pass between the second opening and the return connection when theslide is in the second position.

17. The combination of jack and valve of claim 15, wherein said members include a control chamber, and athrottlebetween the pressure line connection and the .control chamber, said check valve being between the 1i V 19. A hydraulic control apparatus including a valve body member with a slide opening therein, a pressure line connection communicating with said opening, a return connection communicating with said opening, and a jack opening communicating with said slide opening; a slide member in said slideopening and movable longitudinally therein; said members including a control chamber and a throttle between the pressure line connection and the control chamber; said members including fluid control means to direct'the flow of hydraulic, fluid from 7 said line connection to said jack'opening when said slide is in a first position, to direct the flow of hydraulic fluid from the jack opening to the return connection when the slide is in a second position and to prevent the'fiowof fluid to and from the jack opening whenthe slide is in a third position, said means including a by-passwith a control valve between the pressure line connection and the return connection, said means including acheckvalve through which the hydraulic fluid flows to the ja'ckwhen said slide is in said first position, said control valve; being normally loaded to open when the slide is in the second position, and'means to additionally load the control valve when the slide is in the firstlposition by a force that is fluid from the jack to a fluid return line, the improvement,

comprising an adjustable valve with a throttle having an upstream end adaptedto be connected to said pump and a function of the fluid pressure in the control chamber.

20. A hydraulic control apparatus as set forth inclaim 1911 0! use With a double acting hydraulic jack, wherein said body member has a second jack opening, said fluid control means 'placing said control chamber in communication with said second jack opening when said slide is 30 communication with said second jack opening when said in the second position and said return connectiondn slide is in the. first position, said slide having a neutral position between said first and second positions, said throttle having a minimum cross section at said neutral position of said slide with the throttle cross section increasing with movementof the slide in either direction from said neutral position.

21. In an apparatus for controlling the flow of hydraulic fluid through a check valve to a jack from a pump supplying fluid under a given pressure and for returning a downstream end adapted to be connected to said jack, said throttle being variable to control the flow of fluid therethrough to the jack, said adjustable valve being'movable between a first position at which fluid flows through said throttle from said pump to'said jack and a second position at which fluid flows from said jack to said line; and by-pass means including a control valve connected to the upstream end of the throttle and to the, return line, said control valve being loaded by a substantially constant force insuflicient to hold said control valve closed against said pressure whereby when said adjustable valve is in the second position said control valve will open to permit substantially fullfluid flow from the pump to the return line, said by-pass means being connected to the donwstream end of the throttle and to the adjustable valve to additionally load the control valve by a supple.- mental force that is a .function of the pressure ,at the downstream end when said throttle is in the first position totthereby regulate the fluid flow from the upstream end to the return line as a function of the pressure at the downstream end.

549,134 11/42 Great Britain.

FRED E. ENGELTHALER, Primary Examiner. I

THEODORE .G. CRAVER, Examiner. 

14. THE COMBINATION OF A HYDRAULIC JACK AND A SLIDE VALVE THEREFOR, SAID COMBINATION INCLUDING: A HYDRAULIC CYLINDER; A PISTON MOVABLE AXIALLY IN SAID CYLINDER; A CYLINDER HEAD MEMBER CLOSING ONE END OF SAID CYLINDER, SAID HEAD HAVING A FIRST OPENING THEREIN FOR A VALVE SLIDE AND POSITIONED AT AN ANGLE TO THE LINE OF MOVEMENT OF THE PISTON, A SECOND OPENING BETWEEN SAID FIRST OPENING AND SAID CYLINDER, A PRESSURE LINE CONNECTION COMMUNICATING WITH SAID FIRST OPENING, AND A FLUID RETURN CONNECTION COMMUNICATING WITH SAID FIRST OPENING; A SLIDE MEMBER IN SAID FIRST OPENING AND MOVABLE LINGITUDINALLY THEREIN; RESILIENT MEANS URGING SAID SLIDE MEMBER IN A GIVEN DIRECTION IN THE FIRST OPENING; MEANS OPERATIVELY CONNECTED TO THE SLIDE MEMBER AND EXTENDING OUTSIDE THE HEAD MEMBER TO PERMIT SAID SLIDE MEMBER TO BE MOVED IN THE REVERSE OF SAID DIRECTION AGAINST SAD URGING; SAID MEMBERS INCLUDING FLUID CONTROL MEANS TO DIRECT THE FLOW OF HYDRAULIC FLUID FROM SAID LINE CONNECTON TO SAID SECOND OPENING WHEN SAID SLIDE IS IN A FIRST POSITOIN, TO DIRECT THE FLOW OF HYDRAULIC FLUID FROM THE SECOND OPENING TO THE RETURN CONNECTION WHEN THE SLIDE IS IN A SECOND POSITION AND TO PREVENT THE FLOW OF FLUID TO AND FROM THE SECOND OPENING WHEN THE SLIDE IS IN A THIRD POSITION, SAID FIRST POSITION BEING IN SAID DIRECTION FROM THE SECOND POSITION; A CAM FOLLOWER CONNECTED TO THE SLIDE AND POSITIONED IN SAID SECOND OPENING WHEN SAID SLID IS IN THE FIRST POSITION, SAID FOLLOWER FACING IN SAID DIRECTION; AND A CAM OPERATIVELY CONNECTED TO SAID PISTON AND POSITIONED IN SAID SECOND OPENING, SAID CAM BEING POSITIONED TO CONTACT SAID FOLLOWER AND MOVE SAID SLIDE AWAY FROM THE FIRST POSITION WHEN SAID PISTON REACHES APPROXIMATELY THE END OF ITS STROKE. 